The application is based on an application No. 11-107063 filed in Japan, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates generally to image forming apparatuses such as an electrostatic copying machine, a facsimile, and a printer. More particularly, it relates to image forming apparatuses utilizing corona discharges for forming an image.
2. Description of the Related Art
An image forming apparatus such as an electrostatic copying machine is provided with a charging corona discharger for charging a photosensitive drum in order to produce an electrostatic latent image on the photosensitive drum. In the charging corona discharger, corona discharges are induced.
When the corona discharges are induced, ozone or a nitrogen oxide (NOx) is generated. The ozone or the like may degrade the photosensitive drum, resulting in the possibility that a good image cannot be formed.
In order to prevent the photosensitive drum from being degraded, it is considered that an ozone removing device is provided. For example, an air shielding plate provided in an area surrounding the photosensitive drum and suction means for sucking in air from the area surrounding the photosensitive drum, so that air including ozone can be sucked in and removed from the area surrounding the photosensitive drum (see JP-A-61-23168).
When the air shielding plate is provided, as described above, the size of the image forming apparatus is made large. Further, jam processing is difficult to perform. Accordingly, the construction of the apparatus becomes complicated. Further, air is sucked in from the whole area surrounding the photosensitive drum, so that the size of a fan for sucking in the air must be made large in order to efficiently remove the ozone.
An object of the present invention is to solve the above-mentioned technical problems, and to provide an image forming apparatus capable of efficiently preventing a photosensitive drum from being degraded by ozone or the like in simple construction.
In the present invention, ozone or a nitrogen oxide generated when a charging corona discharger induces corona discharges in order to charge the surface of a photosensitive drum does not stay in an area surrounding the photosensitive drum. Therefore, the image forming apparatus is so constructed that an air current is formed toward the circumference of the photosensitive drum. The air current is formed by a mechanism comprising an air fan, an air duct, and preferably a guiding member.
When air flows into the area surrounding the photosensitive drum, and the air is further diffused into a housing from the area surrounding the photosensitive drum, to flow out of the housing, the ozone or the nitrogen oxide does not stay in the area surrounding the photosensitive drum.
Particularly, the ozone or the nitrogen oxide generated in the area surrounding the photosensitive drum can be removed from the area surrounding the photosensitive drum more easily than it is removed by suction.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.